The water glows simply due to the radiation leak from the ancient power core embedded in the bottom of the pool. Someone knew this would happen 5000 years ago, but they were derided for their concerns.

Or, it is…a space ship. Yes, an ancient space ship that crashed into the pool eons ago and has been forgotten.

Relax, it’s just a harmless pool of Protozoa Nim (Nim’s Island)! XD Or it’s just lit underneath. And is it just me, or did the entire pillar collapse EXCEPT FOR the piece underneath them? Is this like one of those Bugs Bunny things where a person saws a hole underneath someone and the whole floor falls except for the piece that should have fallen instead?